The long range objective of this research is to understand the molecular mechanisms by which a protein hormone, human chorionic gonadotropin (hCG), induces granulosa cells to differentiate into luteral cells. The proposed studies focus on catabolic, conformational and rotational changes that occur to hCG after its binds to granulosa cells, and the temporal relationships between observed changes and functional reponses. The studies will utilize granulosa cells obtained from ovaries of intact, immature rats that have been treated for three days with diethylstilbestrol, and then cultured for three additional days with follicle stimulating hormone to promote differentiation and the induction of hCG-receptor. The project will focus on identifying and studying distributional, conformational, rotational and metabolic changes in hCG and its subunits that occur after binding to receptor. Methodologic approaches include use of monoclonal antibodies to hCG, dual radioisotope analyses, immunoaffinity chromatography, reverse phase and size exclusion HPLC, two dimensional exectrophorsis, enzyme linked and radioisotopic immunoassays, electron and light microscopic autoradiography, and kinetic responses in a continuous perifusion system. Response parameters include changes in LH receptor number, ornithine dicarboxylase activity, and production of progesterone, estradiol and cyclic AMP.